Download HIC: ALICE, The Wonderland more or less personal view

2007 APCTP Workshop on
“Frontiers in Nuclear and Neutrino Physics”
HIC: ALICE, The Wonderland
(more or less personal view)
Shin, Ghi Ryang
Dept. of Physics, ANU
Feb. 26-28, 2007
I. Introduction
• HIC(heavy ion collision) Simulation (Au-Au from
BNL)
• Schematic Time evolution 1:
CYM & LGT
Before
Pre-QGP
Hydro
At
PCM & clust. hadronization
expansion
contact
Hadronization
and expansion
NFD
NFD & hadronic TM
- Schematic Time evolution 2:
Thermalization
• Basic data:
RHIC
LHC
E_cm
200 GeV
5.5 TeV
A
Au(197)
Pb(207)
R
6.4 - 7 fm
6.5-7.1 fm
gamma
100
2750
X(=p_d/p_p)
10^-2 - 10^-3
10^-3 – 10^-4
Q_0
1-2 GeV/c
2-3 GeV/c
II. Before the collision
• At Rest:
– R = 1.1 A^1/3 fm
– Nucleon distribution: see textbook on nuclear
physics
• Wood-Saxon model
• Shell model
• Liquid-drop model
• Constant density (Sharp-edge) model
– Parton distribution:
• DIS(ep) scattering: See Halzen and Martin
• At high speed:
– Lorenz contraction with gamma factor.
– Partons may overlap to become CGC(color glass
condensate).
• In general, the parton distribution of a nucleon:
– Momentum distribution:
• CTEQ
• GRV
• MRST
• And so on…: there is website providing the
code.
– No specific space distribution:
• Nucleon distribution within nuclei:
– EKS : see Eskola
– And so on…
• Thus,
– CTEQ X EKS with space
distribution
– GRV X EKS with space
– ….
• Once we know one distribution at
given scale, we can use BFKL or
DGLAP equations.
• Recent development of distribution
(CGC): See excellent reviews by
McLerran, Venugopalan, Mueller,
Blaizot etc.
– Main idea:
• High x parton: sources of Weizacker-Williams
field
• But those fields overlap and fuse together
– Problems:
• Gluon only.
• At rest, those nucleons are independent. At
high speed, they entangle and fuse. But, we
know they should be related by LT and LT
cannot explain the entanglement.
III. At Contact
• Two viewpoints:
– Parton collision: See Eskola
• Two (projectile and target) distributions
overlap
• Partons collide each other
– P_t > Q_0 : escape from parent nucleon
– P_t < Q_0 : stay in the nucleon
• Q_0 : perturbative regime
– CGC shattering: see Krasnitz
• Two CGCs smash and give birth to virtual
partons
• Equation of motion:
• 4 different kinds of partons:
– High p_t and high p_z: jets
– High p_t and low p_z : jets, will travel through
medium
– Low p_t and high p_z : mostly valence partons
– Low p_t and low p_z : soft partons, medium
– NOTE: the collision time is very short
• ~ 0.14 fm/c at RHIC
• ~ 0.005 fm/c at LHC
– Tentative thermalization time is 0.6 - 1
fm/c
IV. Formation of QGP:
Just after a collision
• Very difficult subjets. But we can make
scenarios
• Hawking-Unruh Radiation: Born to be
thermal: see Khazeev et al. or Satz
– Hawking Radiation: near the event horizon,
radiation escape with thermal temp. T ~ g/2pi
– Unruh radiation: From the equivalence principle,
the accelerating particle also radiates with T ~
a/2pi
– Thus strongly decelerating partons while
overlapping radiate in thermal, T ~ a/2pi.
– We know that the nucleons become transparent
as the collision energy goes high.
• Bottum-up scenario: see Mueller at al.
– Soft partons thermalized first
– Hard parton thermalized
– Time scales have been given.
• Collision scenario: see parton cascade
– Partons collide each other to become thermal
– Shuryak claims one collision per parton is enough.
– No collective effects of soft partons
• Weibel Instability : See Mrowczynski
• Color Force Explosion: personal view
– High p_t or high p_z (most likely valence quarks)
quickly escape from the system
– Color charge unbalance in the system
– Substantial color force will exert each other
– We need to look at the ep collision if there is
explosion!!
• And so on :
V. Hydro expansion
• There are many groups working on the
subjects: Japanese group (Hirano, Nonaka,
and so on), Yonsei group, …
• 1D, 2D, 3D hydro
• Recently analytic solutions have been sought
and found:
– 1D: Bjorken expansion
– 2D:
– 3D: ellipsoidal Hubble-like expansion, see
Csorgo
An example of Hubble-like
expansion
• This means that, with small viscosity,
– The expansion is more or less free motion
in particle point of view. Thus a
collisionless transport theory may works
fine.
– While they run free, less virtual partons
eat higher virtual partons to become
constituent partons (quarks or antiquarks
only): see valon theory by Hwa.
We look at v2 : see Lacey
Very different v2 aline nicely with constituent
quarks or antiquarks: which means 1) hadrons
have common partons, 2) the elements are
constituent partons.
VI. Hadronization
• Two ways to make hadron:
– Recombination method:
• Cooper and Frye:
• Fries, Muller, Nonaka, and Bass:
• Greco, Ko, and Levai:
– Fragmentation method:
– Unified view : see Majumder, based on
field theory
VII. Hadron Evolution
• UrQMD works fine
• And so on ….
VIII. Conclusion
Thanks for attention